Advances In Optical Technology Research Articles

Effect of skin optical absorption on speckleplethysmographic (SPG) signals.

Recent advances in optical technology have emerged for measuring blood flow in the extremities using speckleplethysmography (SPG), which may address needs in vascular medicine and other fields. SPG has demonstrated a highly linear response with flow rate, but the susceptibility to differences in skin tone is unclear. Two validation studies using skin-simulating phantoms and a simple clinical protocol were conducted to determine the impact of absorbing skin layers on SPG measurements. Benchtop results demonstrated that the coefficient of determination between known flow rate and SPG was highly linear (R2 = 0.990) and was unaffected by the addition of skin-phantom layers with variable absorption (R2 = 0.996-0.999). Additionally, no significant trend was found between the fit residuals of SPG and flow rate with increasing skin-phantom absorption (R2=0.025, p = 0.29). In clinical testing, no significant difference was found using both a 4-way ANOVA between demographic classifications (F = 0.89, p = 0.45), and a 2-way ANOVA test between lower- and higher-melanin subclassifications (F = 0.4, p = 0.52).

Atlas of Human Retinal Pigment Epithelium Organelles Significant for Clinical Imaging.

PurposeTo quantify organelles impacting imaging in the cell body and intact apical processes of human retinal pigment epithelium (RPE), including melanosomes, lipofuscin–melanolipofuscin (LM), mitochondria, and nuclei.MethodsA normal perifovea of a 21-year-old white male was preserved after rapid organ recovery. An aligned image stack was generated using serial block-face scanning electron microscopy and was annotated by expert readers (TrakEM, ImageJ). Acquired measures included cell body and nuclear volume (n = 17); organelle count in apical processes (n = 17) and cell bodies (n = 8); distance of cell body organelles along a normalized apical–basal axis (n = 8); and dimensions of organelle-bounding boxes in apical processes in selected subsamples of cell bodies and apical processes.ResultsIn 2661 sections through 17 cells, apical processes contained 65 ± 24 melanosomes in mononucleate (n = 15) and 131 ± 28 in binucleate cells (n = 2). Cell bodies contained 681 ± 153 LM and 734 ± 170 mitochondria. LM was excluded from the basal quartile, and mitochondria from the apical quartile. Lengths of melanosomes, LM, and mitochondria, respectively were 2305 ± 528, 1320 ± 574, and 1195 ± 294 nm. The ratio of cell body to nucleus volume was 4.6 ± 0.4. LM and mitochondria covered 75% and 63%, respectively, of the retinal imaging plane.ConclusionsAmong RPE signal sources for optical coherence tomography, LM and mitochondria are the most numerous reflective cell body organelles. These and our published data show that most melanosomes are in apical processes. Overlapping LM and previously mitochondria cushions may support multiple reflective bands in cell bodies. This atlas of subcellular reflectivity sources can inform development of advanced optical coherence tomography technologies.

Introduction to the JSTQE Special Issue on Emerging Applications of Multimode, Multicore and Specialty Fibers

The papers in this special section focus on emerging applications of multimode, multicore, and specialty optical fibers. The papers cover a broad range of advanced optical fiber technologies and applications.

Advanced optical access technologies for next-generation (5G) mobile networks [Invited

Fixed optical transport is the predominant fronthaul technology for 4G mobile access networks, carrying the traffic between the central office and subtended antenna sites. With the new functional splits and related standards introduced in 5G, new capacity and quality-of-service requirements are imposed on optical transport. In this paper, we discuss low-cost high-capacity optical fronthaul solutions enabled by advanced modulation formats and wavelength-agnostic passive wavelength division multiplexing (WDM) technology. As the key component, a low-cost remotely tunable WDM transceiver is introduced, specifically designed on a hybrid InP-polymer platform. We also explain why an Ethernet-based 5G fronthaul solution requires additional means to improve the latency and timing performance of the conventional packet forwarding and multiplexing. We review the recent standardization effort on time-sensitive networking in support of 5G fronthaul and present an FPGA-based implementation providing low latency and low packet delay variation following the latest IEEE 802.1CM specification. These advanced technologies can facilitate an effective packet-optical transport for 5G.

Laser micro- and nano-material processing – Part 2

This special issue of Advanced Optical Technologies (AOT) is dedicated to the field of laser-based micro- and nanostructuring methods.

Job scheduling for distributed machine learning in optical WAN

Large companies operate tens of data centers (DCs) across the globe to serve their customers and store data. On the other hand, many machine learning applications need a global view of such global data to pursue high model accuracy. However, for this Geo-distributed machine learning (Geo-DML), it is infeasible to move all data together over wide-area networks (WANs) due to scarce WAN bandwidth, privacy concerns and data sovereignty laws. Therefore, most Geo-DML systems leverage geo-distributed approaches to train models, where global model synchronization is required between DCs over WAN. With the rapid increase of training data and the model sizes, it is challenging to efficiently utilize scarce and heterogeneous WAN bandwidth to synchronize models. With the advancement of optical technology, network topology becomes reconfigurable in optical WAN, which brings a new opportunity for Geo-DML training over WAN.We propose to optimize Geo-DML training with centralized joint control of the network and reconfigurable optical layers. We respectively prove the intra-job and inter-job scheduling problems are NP-hard and strongly NP-hard. For intra-job scheduling, RoWAN based on deterministic rounding algorithm, is presented to dynamically change the topology by reconfiguring the optical devices, and allocate path and rate for each flow. For inter-job scheduling, delayed SWRT is provided to schedule multiple jobs according to their priorities. The simulations in real topologies show that RoWAN reduces global model synchronization communication time of single iteration by up to 15.54%-48.2% on average in comparison with the traditional solutions. Compared to other three inter-job scheduling approaches, delayed SWRT can reduce the weighted job completion time (WJCT) by about 60%, 44.8% and 28.76%.

Laser micro- and nano-material processing – Part 1

This special issue of Advanced Optical Technologies (AOT) is dedicated to the field of laser-based micro- and nanostructuring methods.

Dense Light Field Coding: A Survey

Light Field (LF) imaging is a promising solution for providing more immersive and closer to reality multimedia experiences to end-users with unprecedented creative freedom and flexibility for applications in different areas, such as virtual and augmented reality. Due to the recent technological advances in optics, sensor manufacturing and available transmission bandwidth, as well as the investment of many tech giants in this area, it is expected that soon many LF transmission systems will be available to both consumers and professionals. Recognizing this, novel standardization initiatives have recently emerged in both the Joint Photographic Experts Group (JPEG) and the Moving Picture Experts Group (MPEG), triggering the discussion on the deployment of LF coding solutions to efficiently handle the massive amount of data involved in such systems. Since then, the topic of LF content coding has become a booming research area, attracting the attention of many researchers worldwide. In this context, this paper provides a comprehensive survey of the most relevant LF coding solutions proposed in the literature, focusing on angularly dense LFs. Special attention is placed on a thorough description of the different LF coding methods and on the main concepts related to this relevant area. Moreover, comprehensive insights are presented into open research challenges and future research directions for LF coding.

Performance assessment of a fast optical add-drop multiplexer-based metro access network with edge computing

Next-generation metro access nodes with edge computing need to be redesigned to co-allocate advanced optical technologies, computing, and storage resources to support the upcoming multiple applications in 5G. In this paper, we present a novel metro access edge computing node based on a fast optical add-drop multiplexer with submicrosecond reconfiguration and control for low-latency operation. We investigate the network performance, the location of the edge computing nodes, and the computing resources dimensioning and utilization in order to fulfill the stringent latency requirement in 5G networks. Network function virtualization and network slicing have been considered in the model to emulate the realistic network operation. Optimization of the network, node location, and computing resources in terms of latency and packet loss ratio is numerically investigated via the OMNeT++ simulator under three different types of 5G applications (Massive Internet of Things, content delivery network, and loss-sensitive traffic). Considering a typical metro access network topology with 20 nodes covering a population of around 1 million, numerical results show that less than 200 µs latency is guaranteed for 5G network applications by deploying more than 6 edge computing nodes with 80 servers for each node.

Optical biopsy of penile cancer with in vivo confocal laser endomicroscopy

IntroductionSurgical management of penile cancer depends on accurate margin assessment and staging. Advanced optical imaging technologies may improve penile biopsy and organ-sparing treatment. We evaluated the feasibility of confocal laser endomicroscopy for intraoperative assessment of benign and malignant penile tissue. Patients and methodsWith institutional review board approval, 11 patients were recruited, 9 with suspected penile cancer, and 2 healthy controls. Confocal laser endomicroscopy using a 2.6-mm fiber-optic probe was performed at 1 or 2 procedures on all subjects, for 13 imaging procedures. Fluorescein was administered intravenously approximately 3 minutes prior to imaging for contrast. Video sequences from in vivo (n = 12) and ex vivo (n = 6) imaging were obtained of normal glans, suspicious lesions, and surgical margins. Images were processed, annotated, characterized, and correlated with standard hematoxylin and eosin histopathology. ResultsNo adverse events related to imaging were reported. Distinguishing features of benign and malignant penile tissue could be identified by confocal laser endomicroscopy. Normal skin had cells of uniform size and shape, with distinct cytoplasmic membranes consistent with squamous epithelium. Malignant lesions were characterized by disorganized, crowded cells of various size and shape, lack of distinct cytoplasmic membranes, and hazy, moth-eaten appearance. The transition from normal to abnormal squamous epithelium could be identified. ConclusionsWe report the initial feasibility of intraoperative confocal laser endomicroscopy for penile cancer optical biopsy. Pending further evaluation, confocal laser endomicroscopy could serve as an adjunct or replacement to conventional frozen section pathology for management of penile cancer.

A new set of eyes: development of a novel microangioscope for neurointerventional surgery

BackgroundEndovascular technological advances have revolutionized the field of neurovascular surgery and have become the mainstay of treatment for many cerebrovascular pathologies. Digital subtraction angiography (DSA) is the ’gold standard' for...

Advanced Optical Imaging of Blood Thrombus

The application of advanced optical imaging technology for platelet biology is in its infancy. In this talk, we shall introduce the potential impact of optical imaging in understanding the roles of platelets in thrombus formation and in hemostasis. We will summarize how techniques in optical imaging has enabled exploration of morphological, molecular and fluidic parameters that determine platelet adhesion, activation and consequent roles in thrombus formation. Finally, we discuss the convergence of multiple imaging modalities towards a complete understanding of platelet roles in thrombus formation.

The multi-PMT optical module for the IceCube-Upgrade

Following the first observation of an astrophysical high-energy neutrino flux with the IceCube Neutrino Observatory in 2013, planning for an upgrade of the detector is progressing, which will expand the capabilities of the detector both at low and high neutrino energies. A substantial contribution to the improved performance is anticipated to be achieved by the application of advanced optical module technology. The multi-PMT optical module, mDOM, consists of 24 3-inch PMTs which provide, amongst others, a large, homogeneous photosensitive area and sensitivity to the incident direction of photons. After an introduction, the current status of the mDOM development is presented with emphasis on the characterization of the photomultipliers under consideration.

Photon Upconverted Circularly Polarized Luminescence via Triplet-Triplet Annihilation.

Circularly polarized luminescent materials are of increasing attention due to their potential applications in advanced optical technologies, such as chiroptical devices and optical sensing. Recently, in all reported circularly polarized luminescent materials, high-energy excitation results in low-energy or downconverted circularly polarized luminescence (CPL) emission. Although photon upconversion-i.e., the conversion of low-energy light into higher-energy emission, with a wide variety of applications-has been widely reported, the integration of photon upconversion and CPL in one chiral system to achieve higher-energy CPL emission has never been reported. Herein, a brief review is provided of recent achievements in photon-upconverted CPL via the triplet-triplet annihilation mechanism, focusing on the amplified dissymmetry factor glum through energy transfer process and dual upconverted and downconverted CPL emission through chirality and energy transfer process.

Gyrolog – Developing a Digital Collection of Gyro Instruments for Historical and Didactical Research

AbstractTechnical artefacts and instruments form an essential part of cultural heritage. If historically analysed and suitably explained, they provide insights into developments and objects that had and still have a significant influence upon our present civilization. Without any explanation and contextualization, however, these objects will remain stubbornly silent, especially if they are technically complex or highly encapsulated.Based on a gyroscope collection at the University of Stuttgart, the Gyrolog project intends to take these instruments out of their black boxes by digital means. These inconspicuous yet indispensable objects of many of today's key technologies (from automatic car navigation to handheld devices) are of prime interest to historians of technology as well as to technical didactics and to technical museums. The project will render the unique gyroscope collection at the University of Stuttgart digitally accessible and, moreover, will virtually unite it with smaller collections at other institutions.Apart from their importance for daily life technologies, gyroscopes have always been of prime military interest as well. Reproducing the artefacts digitally will therefore open further ways to science and technology studies of dual use technologies.Gyrolog aims at a basic digital representation of all gyroscopes found in German collections. At the centrepiece of the project, however, cutting edge imaging and digitalizing technologies will exhibit carefully selected objects literally in depth. By combining advanced animation and optical technologies, Gyrolog seeks to present a unique technical collection in digital format as well as an elaborated methodical approach for exploring complex small technical artefacts.

Hybrid Tamm-surface plasmon polaritons mode for detection of mercury adsorption on 1D photonic crystal/gold nanostructures by total internal reflection ellipsometry

Spectroscopic ellipsometry was used for the generation and study of the hybrid TPP-SPP mode as a sensor probe for the real-time formation of amalgam structures on the surface of a plasmon active gold layer. The Au/Hg amalgam formation features and the mercury atoms' penetration into the gold layer were determined by means of the experimental TIRE data and a regression analysis of a multi-layer model containing the index-profile amalgam layer. The hybrid TPP-SPP mode behavior of the coupled excitations provided more information about the mercury atoms' penetration into the gold layer than the single TPP and SPP resonances did. The present study demonstrated the possibility of using the hybrid TPP-SPP mode to design advanced optical gas sensor technologies.

Surface processing of amorphous optical materials by argon cluster ion beam

The production of a high-quality surface of fused silica is an important task for advanced optical technologies. In this work, the surface of fused silica has been processed by argon cluster ion beam having mean cluster size Nmean ranged from 180 to 1000 atoms/cluster and energy E ranged from 5 to 23.5 keV. The analysis of surface morphology using atomic force microscopy and the spectral power density (PSD) function shows a noticeable smoothing of roughness in different spatial frequency ranges, depending on the cluster ion parameters. To evaluate the processing efficiency, the dependence of the etching rate of SiO2 on the parameters of cluster ions has been investigated. It is shown that the etching rate vetch is determined by the energy per atom in the cluster E/Nmean and it varies from 0.2 to 20 nm/min with an energy change from 5 to 130 eV/atom.

Recent advances in optical technologies for data centers: a review

Modern data centers increasingly rely on interconnects for delivering critical communications connectivity among numerous servers, memory, and computation resources. Data center interconnects turned to optical communications almost a decade ago, and the recent acceleration in data center requirements is expected to further drive photonic interconnect technologies deeper into the systems architecture. This review paper analyzes optical technologies that will enable next-generation data center optical interconnects. Recent progress addressing the challenges of terabit/s links and networks at the laser, modulator, photodiode, and switch levels is reported and summarized.

Single-electron charge sensing in self-assembled quantum dots

Measuring single-electron charge is one of the most fundamental quantum technologies. Charge sensing, which is an ingredient for the measurement of single spins or single photons, has been already developed for semiconductor gate-defined quantum dots, leading to intensive studies on the physics and the applications of single-electron charge, single-electron spin and photon–electron quantum interface. However, the technology has not yet been realized for self-assembled quantum dots despite their fascinating transport phenomena and outstanding optical functionalities. In this paper, we report charge sensing experiments in self-assembled quantum dots. We choose two adjacent dots, and fabricate source and drain electrodes on each dot, in which either dot works as a charge sensor for the other target dot. The sensor dot current significantly changes when the number of electrons in the target dot changes by one, demonstrating single-electron charge sensing. We have also demonstrated real-time detection of single-electron tunnelling events. This charge sensing technique will be an important step towards combining efficient electrical readout of single-electron with intriguing quantum transport physics or advanced optical and photonic technologies developed for self-assembled quantum dots.

Upconverting materials for boosting the development of advanced optical microrheometric techniques

The confluence of technological advances in optics and the need of a deeper understanding of cellular processes have boosted the development of diverse optical microrheometric techniques. These experimental methods have allowed a better understanding of not only the viscoelastic behaviour of cells, but also different intracellular processes. In this work, the fundamentals of the most commonly used optical microrheometric techniques and their more relevant applications in the biological field are expounded for a non-specialist public. In particular, the promising and emerging use of upconverting luminescent particles as probes in this field is highlighted, as they could be the cornerstone of the development of new methods or the improvement of already existing microrheometric techniques.